1. Field of the Invention
The present invention relates to an instantaneous clamping/unclamping mechanism for a CNC machine tools, and more particularly, to a clamping/unclamping machine for a CNC machine tools which can instantaneously separate a tool from a holder and replace it with another one without miss operation.
2. Description of the Prior Art
A conventional tool clamping/unclamping mechanism for a CNC machine tools comprises an tool pot in a spindle; a tool pot; a compression spring installed between the spindle and the tool pot; a oil cylinder mounted over the tool pot with a piston and a piston rod passing through the cylinder; and an adjusting screw attached to the tool pot from the bottom of the piston rod. With such constitution a clearance is formed between the tool pot and the oil cylinder helpful for preventing miss operation of the tool pot, such as dropping a tool in the case the tool is not to be replaced. When the time comes for a tool to be separated, being actuated by the oil pressure, the piston rod has to travel a certain distance in advance in order to eliminate the clearance, and continues to perform a stroke for tool replacement. However, there are disadvantages inherent to the constitution of such clamping/unclamping mechanism i.e.:
(1) A time delay is produced due to the above described piston travel procedure for eliminating the clearance before tool unclamping to take place. Should the time delay be too long, a tool arm which has been moved to a position ready for performing its function, is apt to hit the tool which is still on the tool pot and be damaged therefor; or, should the time delay be too short, a tool is separated from the tool pot and dropped on the ground before it is taken up by the tool arm whereby causing a dangerous state.
(2) The clearance influences greatly the performance of tools clamping/unclamping, the tedious work of adjusting the clearance is very important and sophisticated that has to rely on a skilled and experienced workman to perform. Even so, the occurrence of an error is inevitable. Besides, the clearance is required to re-adjust in the case the mechanism is detached and re-assembled for maintenance.
(3) The oil cylinder and the tool arm are actuated and controlled by different systems. However, the action of the two systems is difficult to keep pace with each other for performing accurate and highly efficient tool unclamping.
It is an object of the present invention to provide an instantaneous clamping/unclamping mechanism for a CNC machine tools by employing one oil cylinder and two pistons working mode to perform two stage procedures of tool separating from a spindle, which can further precisely keep pace with the clamping/unclamping procedure to be carried out by a tool arm so as to prevent possible accidental errors inherent to a conventional mechanism as described above and achieve a reliable instantaneous clamping/unclamping effect for a CNC machine tools.
To achieve the object mentioned above, the instantaneous clamping/unclamping mechanism with two stage procedure tool separating function comprises the components of a oil cylinder with a piston rod passing through its inner part and engaged with a first piston for tool separating installed therein, a second piston for tool presetting installed at the bottom of the first piston and is in slidable relation with the piston rod. The space in the oil cylinder is therefore separated by the two pistons into upper, middle and lower three oil flowing chambers. Further, an adjusting screw is provided at the bottom of the piston rod and is connected with the tool pot. Two mechanical valves are provided for controlling the direction of oil flow for operating the piston rod to perform two stage procedures of tool separation. The position of the two valves is controlled by a valve position changeover mechanism. A driving means for the tool arm is interconnected with the valve position changeover mechanism to perform close joint operation thereby achieving well matched action of tool separation and replacement.